Also known as: Adrenaline; Noradrenaline; Dopamine; Epinephrine; Norepinephrine; Urinary free catecholamines
Name: Plasma and urine catecholamines
Related tests: Plasma free metanephrines, Urine metanephrines
Why get tested?
To diagnose phaeochromocytoma or other neuroendocrine tumours
When to get tested?
When there are symptoms such as severe headaches, persistent or episodic high blood pressure, a rapid heartbeat and increased sweating, suggesting increased release of catecholamines
What type of sample is needed?
Blood taken from a vein in the patient’s arm, or urine collected over 24 hours
Is any preparation needed for the test?
The results of these tests are affected by some medicines, foods and stress. It is therefore important to tell your doctor about any treatments you are taking and to follow the instructions given before the test
What is being tested?
Catecholamines are a group of hormones produced by the medulla (inner part) of the adrenal glands. The adrenal glands are small, roughly triangular organs located on top of the kidneys. The primary catecholamines are dopamine, epinephrine (adrenaline) and norepinephrine (noradrenaline). These hormones are released into the bloodstream in response to physical and psychological stress. They help transmit nerve impulses, increase blood levels of energy sources such as glucose and fatty acids, and widen the bronchioles and pupils. In addition, norepinephrine increases vascular tone and blood pressure, and epinephrine increases the heart rate and metabolism. Once they have done their job, these hormones are metabolised into inactive compounds. Dopamine becomes homovanillic acid, norepinephrine is broken down into normetanephrine and vanillylmandelic acid (VMA), and epinephrine becomes metanephrine and VMA. Both the hormones and their metabolites are excreted in the urine.
Normally, catecholamines and their metabolites are present in the blood in small, fluctuating concentrations that rise noticeably only after stress. Phaeochromocytoma and other neuroendocrine tumours can produce large amounts of catecholamines, which can be found in both blood and urine. This can cause persistent or episodic high blood pressure, leading to severe headaches and sometimes palpitations, increased sweating, nausea, vomiting, anxiety and tingling in the hands and feet.
About 90% of phaeochromocytomas are located in the adrenal glands; some are malignant, but most are benign and do not spread, although they continue to grow. If left untreated, the symptoms get worse and the tumour grows, causing kidney and heart damage and increasing the risk of heart attack and stroke.
Plasma and urine catecholamines can help diagnose phaeochromocytoma. Although it is a rare form of cancer (about 1 in 800 cases tested in the USA is positive), it is still important to test for it because it is a potential cause of curable high blood pressure. In many cases the tumour can be surgically removed and/or treated to reduce the amount of catecholamines produced, and so reduce or eliminate the associated symptoms and complications.
The catecholamine test measures the concentration of epinephrine, norepinephrine and dopamine in the blood and urine. The plasma test shows the concentration of these molecules at the time the sample is taken, while the urine test shows the amount excreted over 24 hours.
How is the sample collected?
The urine sample is collected over a 24-hour period. It is important that the sample is kept refrigerated during this time.
The blood sample is taken from a vein in the patient’s arm. Opinions differ on how the sample should be taken. In some centres the patient is asked to lie down and relax for 15-30 minutes, and the sample may be taken in this position. In other centres the patient is simply seated, with no or only a short period of rest beforehand
Is any preparation needed for the test?
Both the urine and the plasma tests can be affected by some foods, medicines and stress. It is therefore important to tell your doctor about any treatments you are taking and to follow the instructions given before the sample is collected
How is it used?
When is the test requested?
How is the test result interpreted?
Is there anything else I should know?
How is it used?
The catecholamine test is used to help diagnose phaeochromocytoma in patients with symptoms. It is also used to monitor treatment after a phaeochromocytoma has been found and surgically removed, and to check for recurrence. The plasma test is used mainly when the patient has chronic or acute high blood pressure, because catecholamines do not stay intact in the blood for long: they are used, metabolised and/or excreted. The urine test measures the total amount of catecholamines produced over 24 hours. Even though catecholamine concentrations do not fluctuate significantly over this period, the urine test can detect overproduction that the plasma test misses. The plasma and urine tests may be requested separately or together.
The test is sometimes also requested for patients without symptoms who have been found to have an adrenal or neuroendocrine tumour on an ultrasound scan done for other reasons, or for patients with a family history of phaeochromocytoma.
When is the test requested?
When the doctor suspects that the patient has a phaeochromocytoma or wants to rule it out. It may be requested when the patient has high blood pressure with headache, excessive sweating, hot flushes and a rapid heartbeat, or when high blood pressure does not respond to conventional treatment, as often happens in patients with phaeochromocytoma.
The test is also used to monitor patients who have previously been treated for a phaeochromocytoma.
How is the test result interpreted?
Because the catecholamine test is quite sensitive to outside interference and phaeochromocytoma is quite rare, false positives are common; for this reason further tests must be carried out when the test is positive. The doctor must have a complete picture of the patient’s physical and mental health and of the treatments and foods they are taking. If an interfering substance or mental state is identified, the doctor should have the test repeated once the cause of interference has been removed.
Plasma and/or urine metanephrine tests may also be requested to confirm the diagnosis.
If catecholamine levels are raised in patients who have previously had a phaeochromocytoma, either the treatment was ineffective or the tumour has come back.
If catecholamine concentrations are normal in both blood and urine, the person is unlikely to have a phaeochromocytoma, although this type of tumour sometimes does not produce catecholamines continuously; in fact, a person may have normal catecholamine values if they have not recently had high blood pressure, even if the tumour is present.
Is there anything else I should know?
Catecholamines give no information about the location or number of masses, or whether the tumour is benign or malignant. In addition, although catecholamine concentrations tend to rise as the tumour grows, they do not always give clues about the size of the tumour.
Many substances can interfere with the test result. It is important that the doctor knows about the patient’s treatments and diet, so that interfering substances can be stopped before the test. These substances include: paracetamol (acetaminophen), aminophylline, amphetamines, appetite suppressants, coffee, tea or caffeine in other forms, chloral hydrate, clonidine, dexamethasone, diuretics, epinephrine, ethanol (alcohol), insulin, imipramine, lithium, methyldopa (Aldomet), MAO (monoamine oxidase) inhibitors, nicotine, nitroglycerin, nose drops, propafenone (Rythmol), reserpine, salicylates, theophylline, tetracyclines, tricyclic antidepressants and vasodilators. The effects of these substances can vary from patient to patient and are often unpredictable.
1. Can phaeochromocytoma be prevented?
2. Is it really necessary to collect urine over 24 hours?
3. Can the patient’s psychological state really interfere with the test result?
1. Can phaeochromocytoma be prevented?
No, but in many cases the tumour is benign and does not come back after surgical removal.
2. Is it really necessary to collect urine over 24 hours?
Yes, it is needed for the test to be accurate, because catecholamines are released at different times and a single sample may not be enough.
3. Can the patient’s psychological state really interfere with the test result?
Yes, because the adrenal glands respond to stress. In an anxious or frightened patient catecholamine concentrations rise